Artificial structure and method for producing same



May 7, 1940. E. v. LEWIS 2.199.411

ARTIFICIAL STRUCTURE AND METHOD FOR PRODUCING SAME Filed Nov. 1, 1958 3 Sheets-Sheet 1 y 7. 1940- E. v. LEWIS 2.199.411

ARTIFICIAL STRUCTUREAND METHOD FOR PRODUCING SAME Filed NOV. 1, 1958 3 Sheets-Sheet 2 ATTORN EY E. V. LEWIS May 7, 1940.

ARTIFICIAL STRUCTURE AND METHOD FOR PRODUCING SAME 3 Sheets-Sheet 3 Filed Nov. 1,, 1938 INVENTOR ATTO R N EY Patented May 7, 1940 UNITED STATES ARTIFICIAL STRUCTURE AND ME'I'IIODFOB PBODUOIN G 51mm Everett Vernon Lewis, Wilmington, DeL, aasignor to E. I du Pont de Nemours a Company, Wilmington, Del., a corporation of Delaware Application November 1, 1938, Serial No. 238,212

13 Claims.

- structures; more particularly, it relates to improved filaments, yarns, ribbons and like structures of synthetic linear polyamides which have a reduced residual shrinkage.

Carothers in U. S. Patents Nos. 2,071,250, 2,071,251 and 2,071,253 describes an entirely new class of compounds, i. e., synthetic linear polymers, and filaments comprising them. Of these synthetic linear polymers, the polyamides are particularly interesting. The synthetic linear polyamides are of two types, those obtainable from monoaminomonocarboxylic acids, and those obtainable from the reaction of suitable diamines with dibasic carboxylic acids. The diaminedibasic acid derivatives are more fully described in U. S. Patent No. 2,130,948. For convenience, this invention shall be discussed in terms of polyhexamethylene adipamide which is obtainable from the reaction of hexamethylene diamine with adipic acid, although it is not so limited.

These synthetic linear polyamide filaments, and like structures, whether spun from a melt or from a solution, are usually coldv drawn (stretched in the solid state) to a ratio of initial to final length of 1:3 to 1:425 (300%-42S%) whereupon their alongation is greatly reduced and they exhibit orientation of crystals along the fiber axis as evidenced by X-ray investigation. This cold drawing operation improves the properties of these filaments, e. g., increases their tensile strength, elasticity and resistance to stretch.

These oriented synthetic linear polyamide filaments, yarns, etc., have the unusual property of becoming set upon exposure to steam, hot water or other non-solvent, mild swelling agents for the polyamide hereinafter referred to as setting agents. After being set, these structures tend, when deformed, to return to the shapeor condition in which they were set after the deforming force is removed. This setting action is more fully described in the co-pending U. S. patent applications of John Blanchard Miles, Jr., Serial No. 125,941 filed February 15, 1937, and Serial No. 227,014 filed August 26, 1938.

Advantage is taken of this property in obtaining knitted, woven and pile fabrics of excellent properties by setting them in any desired shape, e. g., stitch formation, shape, etc. This setting action is not easily reversible. In other words, the effects of a setting treatment on a polyamide yarn or fabric cannot be overcome by a second treatment of equal severity. If the second treatment is made more severe, e. g., by means of a treatment at a higher temperature and/or by a more prolonged treatment the yarn or fabric can be set in another form fairly successfully, but if the first setting treatment is carried out at temperatures above 90 C. the structure can be reset only with the greatest difllculty. For this reason it is usually preferred that these polyamide yarns be first subjected to setting conditions in the form ultimately desired in the fabric. Advantage is taken of this property in the manufacture of stockings from synthetic linear polyamides as is more fully described in the co-pending application of John Blanchard Miles, Jr., Serial No. 216,409 filed June 28, 1938.

These oriented synthetic linear polyamide yarns have a high residual shrinkage" (approximately 10%) and as a result when fabrics comprising them are subjected to hot, wet conditions, e. g., boil-off or dyeing operations, they shrink excessively. This high shrinkage is very objectionable, and it is consequently diflicult to obtain the proper size of manufactured goods, for example, leg size in full-fashioned hosiery. By the term "residual shrinkage" is meant the decrease in length which a filament or yarn undergoes when subjected" in a relaxed condition to hot aqueous treatment, with or without detergenw at a temperature of 95-100 C. for several minutes. In determining residual shrinkage a measured sample is subjected to the shrinking treatment described above, dried in a relaxed condition, and its length determined at the same humidity and temperature as the initial measurement.

It has been known, prior to the present invention, that yarns or filaments of synthetic linear polyamides produced in the above-described manner may be shrunk by treatment with hot water, or steam it maintained under a low tension, for example, in the form of skeins. By pretreatment of such yarns or filaments with hot water or the like, excessive shrinkage of the fabric is avoided but the yarn is caused to set, and such set yarn when knit into fabrics tends to result in irregular and poor stitch formation. This is thought to be the result of the setting effect, above described, which prevents the yarn from readily taking and maintaining the shape imposed by the sinkers, dividers and needles in a knitting machine and from being readily set in this shape by a subsequent setting operation. Fabrics knit from such yarn often have such poor and irregular stitch formation as to give the appearance of a lace.

It is, therefore, an object of this invention to reduce the high residual shrinkage of oriented synthetic linear polyamide filaments and yarns by the application of heat in the absence of water or other non-solvent swelling agents for the poly-.

amides.

It is a further object of this invention to reduce the high residual shrinkage of oriented synthetic linear polyamide filaments and yarns without setting them, I

It is a further object of this invention to reduce the high residual shrinkage of oriented synthetic linear polyamide filaments, yarns, and the like without introducing the tendency towards poor flexible sheet steel member 2I.

knit stitch formation resulting from shrinkage by means of agents having a setting action.

It is another object of this invention to produce improved filaments, yarns, ribbons, and like structures of synthetic linear polymers which have a reduced residual shrinkage, and which structures will be capable of being readily set by exposure to setting agents.

Other objects of the invention will appear here,- inafter.

It has now been found that if oriented synthetic linear polyamide filaments or yarns are subjected to dry heat, that is, heated in the absence of water, steam .or other mild swelling agents for the polyamide to a temperature of over 100 C. while under a low tension they will shrink rapidly, and the residual shrinkage is very materially reduced. Furthermore, yarn shrunk in this manner with a dry heat is not materially set and can be knit or woven in the fabrics with good stitch formation.

The details of the invention will become more cl'early apparent by reference to the accompanying illustrations when taken in connection with the following detailed description.

In the illustrations:

Figure l is a diagrammatic perspective view showing one form of device which is adapted to heat shrink yarn in accordance with the principles of the present invention.

Figure 2 is a perspective view of the hot plate shown in Figure 1 of the drawings.

Figure 3 is a diagrammatic perspective view of another modification of apparatus suitable for use in accordance with the present invention.

Figure 4 is a cross-sectional view of the heating element shown in Figure 3.

Figure 5 is still another modifiedform of apparatus suitable for usein carrying out the present invention.

Referring to Figure 1 of the drawings, reference numeral II designates a package of yarn I3. The yarn I3 is shown passing from the package I I, through a stationary yarn guide I5, over a positively driven guiding roller I1, and through a tensioning device I9. The tensioning device I9 comprises a smoothsurfaced rigid base and a member 2I is pressed against the top surface of the rigid plate so as to lightly clamp the yarn I3 between these two elements. The flexible sheet steel member 2| is positioned in grooves 23 in' rigid frame members attached to the rigid plate in any desired manner. The plate 2| may be held in position at any desired point in the grooves 23 The sheet steel heating plate 21. The heating plate is provided with a pair of electrical resistance heating elements II and 33 whereby to heat it, thus maintaining the groove 20 at any desired temperature.

The yarn I3 is shown passing from the groove 2! about a freely rotatable roller II, thence through a stationary yarn guide 31, and then through a reciprocating yarn guide 30 which is adapted to traverse the yarn backward and forward across a bobbin 0 whereby to build the yarn package 4|. The bobbin 3 is preferably so mounted as to be driven at a constant yarn speed, c. g., surface driven.

Referring to Figure 2 of the drawings, the heating block 21 is illustrated in greater detail showing openings 2! in which heating elements may be positioned. These heating elements may comprise conduits through which a heating medium may be passed, or electrical resistance elements, or any other desired heating means.

Referring now to Figures 3 and 4 of the drawings, the yarn 53 is shown passing from the yarn package 5i, through a stationary yarn guide 55, through a yarn tensioning device. The yarn tensioning device comprises a rigid, smooth-faced plate 51, support not shown, and a thin. flexible steel plate 59. The flexible plate 50 is attached to the pivot arm 62. The pivot arm 62 is pivoted to a rigid frame member 6|. The weight 83 may be positioned at any desired point along arm 82 to suitably vary the pressure with which the flexible plate 59 is pressed against the rigid plate 51. The yarn is shown passing from the tensioning device through groove B1 of the curved heating element 65. The element 65 may be heated by means of high pressure steam, or any other desired liquid or gaseous heating medium. The heating medium is passed through element 65 by means of inlet conduit II and outlet conduit 89, which conduits are connected to a hollow space in element 65. The fiow of the heating medium may be controlled by means of valves I3 and I5 and the pressure of the heating medium can readily be determined by means of gauge I1. After passing through groove 61 of heating element 85 the yarn is shown passing over the roller 83 which is adapted to rotate in contact with the positively driven roller 8| which is partially im-- rnersed in a tank 19 containing a finishing for the yarn. The roller 83 is adapted to apply the desired amount of a size composition to the yarn prior to its being wound in the form of a package. The yarn is then shown passing over guide roller 85, through a fixed guide '6 and thence through a traversing guide 81 which is traversed back and forth to position the yarn on the surface driven bobbin iii in the form of a wound cake 89.

Referring now to Figure 5 of the drawings, a yarn or filament I03 is shown passing from the wound package IIlI through stationary yarn guide I05,thence through a yarn tensioning device simi- The drawing assembly comprises the positively driven roll II! and the freely rotatable separator roll I2I and a second identical pair of rolls I23 and I25. The yarn is shown passing first about .the positively driven roll IIS and thence around it and the separator roll I2 I for a sufllcient number of turns to prevent slippage of the yarn. The

yarn is thenv shown passing to the positively u driven roll I23, thence around the separator roll I25 in the same manner as described for rolls II9 and I2I. The thread is then shown passing over the hard-rubber covered head roll I21 and thence through the groove I29 of the hot plate I28. Electrical resistance elements I3I and I33 are provided for the heating of the hot plate I28 and the groove I29.

After passing through the groove I29 of the hot plate the yarn is shown passing through a stationary yarn guide I35, over a size applying roller I39 which is rotated by contact with the positively driven roll I39 partially immersed in the size bath Ill and thence through a stationary yarn guide I43, and through the traveler of a ring twisting machine. The traveler I45 is positioned about reciprocating ring I41 and the pirn I49 is rotated by means of a belt I5I and pulley I53 at a constant angular speed.

The following detailed examples illustrate certain methods whereby yarns or filaments may be heat shrunk in accordance with the present invention. These examples are illustrative and not to be taken as limitative of the details of the invention.

Example I A 45-denier, 15-filament polyhexamethylene adipamide yarn'cold drawn 410% and having a residualshrinkage of about 11% was drawn from a package II through the heat shrinking apparatus shown in Figure 1 of the drawings by the surface driven bobbin 43. The tensioning device I9 was adjusted to impart a constant. total tension of 3 grams to yarn leaving it. The temperature of the heating plate and of the groove 29 was maintained at approximately 200 C. The length of the block in the direction of the groove 29 was approximately 4 inches. The bobbin 43 was driven to wind up the yarn at a constant speed of feet per minute. thrunk in this manner was found to have a residual shrinkage of 1.5% as compared to its original residual shrinkage of 11%. Furthermore. this yarn when knit into the leg of a full-fashioned stocking gave excellent stitch formation. and the stocking after. boarding, boil-off and dyeing operations was of the proper size.

Example II A 45-denier, 15-filament polyhexamethylene adipamide yarn cold drawn 348% having a residual shrinkage of about 10% was drawn through the heat shrinking and size applying apparatus illustrated in Figure 3 at a uniform speed by the surface driven bobbin 9I. Steam at a pressure of pounds per square inch was passed through the heating element 55 which was approx mately 24 inches long. The yarn tension ng device 51 was adjusted to impart a uniform total tension of 5 grams to the yarn. The yarn was drawn through the heating element at a speed of approximately 9'70 feet per minute. The outwardly curved surface of the heating element 65 kept the yarn in intimate thermal contact with the surface of the groove 61 during its entire passage through groove 61 thus increasing its thermal efficiency in heating the yarn. The yarn, heat shrunk in this manner, was found to have its residual shrinkage reduced from 10% to about 1.3%. The heat shrunk yarn was knit into the leg of a full-fashioned stocking fabric and exhibited excellent stitch formation. Other similarly shrunk oriented polyhexamethylene adipamide yarn was used for the heel, sole and 'welt. The stocking fabric so knit was then looped, seamed The yarn heat and topped in the usual manner, wet and carefully placed upon a stocking form and subjected to saturated steam at 100 C. for five minutes. The stocking was allowed to cool, removed from the form, scoured, dyed and rinsed in the usual manner and reboarded to remove the superficial wrinkles. The stocking so obtained was found to have excellent stitch formation. marvelous elastic properties and was wringle-free and substantially the same size as knit.

Example III A -denier, 11-filament undrawn polyhexamethylene adipamide yarn was passed through the drawing, heat shrinking and size applying apparatus illustrated in Figure 5 of the drawings. The tensioning device 51 was adjusted to impart a total tension of 12 grams to the yarn leaving it. The yarn then passed over the roller III to the draw roll H9, thence about it and the separator roll I 2I and thence to the draw roll I23 and separator roll I25. The draw rolls H9 and I 23 were positively driven at a ratio of peripheral speeds of 1:4.1 respectively. Thus the yarn in passing from the roll II9 to the roll I23 was stretched to 4.1 times its original length (cold drawn 410%). This oriented 33-denier yarn then passed over the head roll I21 which was constructed of hard rubber and wh ch had a surface speed 2% greater than that of the draw roll I23. The head roll I21 served to pull the yarn from the draw roll I23 and deliver it to the groove I29 of heating plate I28, at a uniform rate and at substantially zero tension.

The temperature of the block I28 was maintained at approximately 225 C. and the length of the block in the direction of the groove was approximately 3 inches. The speed of the yarn passing through the groove I29 was approximately 28 feet per minute and was under a total tension imparted to the yarn by the ring twister of approximately 2 grams. The drawn and heat shrunk yarn produced in this manner was found to have a residual shrinkage of about 1.7% as compared to a residual shrinkage of 11% for similarly drawn unshrunk yarn. The heat shrunk yarn so produced was found to give well formed needle and sinker loops when knitted into a fabric. The shrunk yarn, or fabrics comprising it, was easily set by a mild setting treatment in any desired conformation.

To accomplish the heat shrinkage of oriented synthetic linear-polyamide yarns according to this invention. it is essential that the temperature of the yarn be raised to the proper point and that the tension on the yarn be low; i. e., the yarn be free to shrink. The temperature imparted to the yarn to promote heat shrinkage should usually be above 100 C., and preferably between about 120 C. and 180 C. The preferred limits for the heat shrinking of oriented polyhexamethylene adipamide yarns are C.- C. The optimum temperature of the heating surface to impart the proper temperature to the yarn will depend on the speed of the yarn, the length of the heating surface and the denier of the yarn. It will also depend on the efiiciency of the thermal contact between the yarn and the heating surface. The proper temperature for the heating surface can easily be determined by trial for any given arrangement and yarn speed. For example, in the arrangement illustrated in Figure 1 of the drawings, if the length of the block is 8 inches, the yarn speed 1500 feet per minute, the

residual shrinkage of a 45-denier oriented linear 15 polyamide yarn is reduced from about 10% to about 2% when the temperature of the block is 255 C. When lower yarn speeds, for example, 200 feet per minute, are employed the same reduction of residual shrinkage is obtained when the temperature of the block is only 200 C.

The effect of good thermal contact by the thread with the heating element is an important factor. This effect is illustrated by comparing the conditions described in Example I with those described in Example II in which the curved groove giving intimate thermal contact was used. In Example I the time of contact of the yarn with the heated surface was approximately 0.17 second. and in Example II it was about 0.12 second. The temperature of the straight-grooved block was raised to about 200 C. whereas that of the curved-grooved element shown in Figure 2 was only .180 C. and even though the time of contact in the latter was shorter comparable reductions in residual shrinkage were obtained.

The residual shrinkage remaining in the yarn is approximately a linear function of the tension in the range of tensions from 0.05 to 0.4 gram per denier. When using the apparatus illustrated in Figure 1, when two portions of the same 50-denier oriented polyhexamethylene adipamide yarn were shrunk with the temperature of the block 200 0., the length of the slot 4 inches, and the yarn speed 100 feet per minute, but under tensions of 3 grams and grams respectively, the residual shrinkages of the resultant yarns were 2% and 5% respectively.

Heat shrinkage need not be carried out on a yarn moving continuously. Yarn can be wound into skeins or on to packages, preferably collapsible packages, and treated with heat in an oven. However, it is preferred to carry out heat shrinkage on continuously moving yarn since the heating and shrinkage of yarn in packages is not uniform.

There are, of course, many modifications which may be made in the method and apparatus for the continuous heat shrinkage of yarns. The yarn need not be heated by contact with a hot metal but may be heated by passing it in contact with any other rigid heated element, or by passing the yarn through a liquid which does not have a swelling action on the yarn. Tetrachlorethylene and other substituted hydrocarbons with low vapor pressure can be used for this purpose. Water, or other compounds, such as methanol, ethylene glycol, glycerol and aniline, have a swelling action on the polyamide and are not suitable either in the liquid or gaseous phase for use in heat shrinkage of oriented polyamide yarns in accordance with the present invention. Heated air or other gases may be used to heat shrink yarn in accordance with the present invention.

Itis to be understood that the practice of my invention includes the use of air under atmospheric conditions, e. g., of relative humidities commonly encountered, heated to temperatures effective in the practice of this invention. Heated air substantially unsaturated with moisture vapor has only a slight setting action on these synthetic linear polyamide yarns so that the yarns so shrunk may be readily knit or woven into fabrics with any desired stitch formation.

Since it is essential that the tension on the yarn be low during the heat shrinkage thereof, it is sometimes desirable when taking yarn from a package which will not deliver the yarn at a sufficiently low tension to pull the yarn by suitable rolls from such a package and feed it to the region where heating and shrinking takes place at a rate sufficiently greater than that with which it is withdrawn from the said region so as to allow for proper shrinkage to take place or to use a light, slip-driven wind-up with such a feed. While this invention has been described with particular emphasis on yarns consisting solely of synthetic linear polyamide filaments it is also applicable to mixed yarns comprising these polyamide filaments in combination with other textile filaments. Similarly, yarns comprising staple length synthetic polyamide fibers alone or in combination with other textile fialments or fibers may be dry shrunk according to this invention. Likewise, if desired, fabrics comprising these synthetic linear polyamide filaments may be shrunk according to this invention.

Many advantages accrue from a practice of the invention. For the first time it is possible to materially reduce the residual shrinkage of a textile yarn by a process which does not involve wetting out with water or other liquid. Furthermore, this shrinkage occurs very rapidly. It is, therefore, possible to shrink these oriented synthetic linear polyamide yarns continuously at very rapid rates and under controlled conditions. Since the yarn is not wet during this shrinking process, the slow, cumbersome, power-consuming and expensive drying operations are eliminated. Similarly, more than one end of yarn may be shrunk simultaneously and the yarns passed directly from the shrinking zone to further textile operations without being wound on a package. For example, a warp of oriented polyhexamethylene adipamide yarn may be passed in contact with a wide heated metal plate, thus shrinking all the ends simultaneously and uniformly. This warp may then pass directly to a beam for use in a loom.

The oriented synthetic linear polyamide yarns shrunk according to the invention are superior to unshrunk yarns because they permit the manufacture of fabrics of the proper size which do not shrink upon being boiled off or dyed or during subsequent laundering operations. These heat shrunk yarns are superior to previously known shrunk polyamide yarns since they are sufflciently unset to permit their use in weaving or knitting fabrics with uniform and desirable stitch formation. Furthermore, they can be readily set in any desired conformation by a subsequent setting treatment.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited except as set forth in the appended claims.

I claim:

1. A dry-heat-shrunk synthetic linear polyamide filament characterized in that it is sufficiently unset to permit its use in weaving or knitting fabrics of uniform stitch formation.

2. A dry-heat-shrunk polyhexamethylene adipamide filament characterized in that it is sufficiently unset to permits use in weaving or knitting fabrics of uniform stitch formation.

3. A dry-heat-shrunk synthetic linear polyamide filament having a residual shrinkage not to exceed 5%, characterized in that it is sumciently unset to permit its use in weaving or knitting fabrics of uniform stitch formation.

4. A dry-heat-shrunk synthetic polyhexamethylene adipamide filament having a residual shrinkage not to exceed 5%, characterized in that it is sufficiently unset to permit its use in weaving or knitting fabrics of uniform stitch formation.

5. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises heating said structures in the absence of a swelling medium for said polyamide.

6. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises heating said structures under a low tension in the absence of a swelling medium for said polyamide.

7. The process of reducing the residual shrinkage of synthetic linear polyamide structureswhich comprises heating said structures under a tension not to exceed 0.3 gram per denier in the absence of a swelling medium for said'polyamide.

8. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises heating saidstructures under a low tension at a temperature above C. in the absence of a swelling medium for said polyamide.

9. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises continuously passing a synthetic linear polyamide yarn in contact with a dry heated surface. I

10. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises continuously passing a synthetic linear polyamide yarn in contact with a dry surface heated to a temperature above 100 C.

11. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises continuously passing a synthetic linear polyamide yarn in contact with a dry surface heated to a temperature above 100 C. for a sufficient period of time to reduce the residual shrinkage to at least 5%.

12. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises continuously passing a synthetic linear polyamide yarn under a low tension in contact with a dry surface heated to a temperature above 100 C.

13. The process of reducing the residual shrinkage of synthetic linear polyamide structures which comprises continuously passing a synthetic linear polyamide yarn under a tension not to exceed 0.3 gram per denier in contact with a dry heated surface for a sufficient period of time to reduce the residual shrinkage to at least 5%.

EVERETT VERNON LEWIS. 

